In this section I'll try to describe what my research is all about. As you might have gusees from the "home" page, my main interest is climate variability, especially in the past, and that tree-rings are my major tool. If you want to have some background to why knowledge about climate change and variability is important, go ot the Climate Research section. More information about dendroclimatology and the steps in a dendroclimatological study can be found in other sections (just click away).

My research is focused on spatial and temporal climate variability in northern Europe (mainly Fennoscandia) and Asia (mainly China) during the last couple of thusand years, using tree rings as high to low resolution climate proxies. I have studied the influence of climate on tree growth and reconstructed past climate variability on local to regional scale. By collecting tree-ring data from a wide range of environments, where tree growth is limited by different climatic parameters, I have reconstructed temperature, precipitation, drought and the atmospheric circulation back in time.

Old pine forest from the central Scandinavian Mountains

During my years as a postgraduate student and postdoctoral researcher, I built a network of tree-ring chronologies in Scandinavia suitable for making climate reconstructions on local to regional scales for the past 500 to 3500 years. Scots pine tree-ring with data from the central Scandinavian Mountains (CSM) have, for instance, used to reconstruct summer temperatures for the past 3.600 years.

Furthermore, the CSM was used in a tentative comparison between Swedish and Tibetan Plateau tree-ring data, where the resuts showed good promises for further studies of climate teleconnection between the two regions. Together with Professor Deliang Chen, RCG, I reconstructed winter precipitation in central Scandinavia for the past 500 years using tree-ring data, which is the fist of its kind in northern Europe. Together with colleagues from Stockholm University, I assessed a new (and improved) method of reconstructing Fennoscandian temperatures for the last 1600 years with good spatial representation

Presently my main interest is in large-scale atmospheric circulation over the North Atlantic, and how it affects climate in the region. Together with Prof. Chris Folland and co-workers at the MetOffice in UK, I reconstructed the summer North Atlantic Oscillation (SNAO) back in time for several centuries. Now I 'm looking at possible teleconnections between the SNAO and climate in Asia tgether with scientists from China.

Together with Professor Peter Jansson, Stockholm University, tree-ring and atmospheric circulation data has been used to reconstruct past variations in mass balances of Scandinavian glaciers. This is an important piece of information needed to make predictions about glacier status in a changing climate. This work will continue, where the role of the atmosphere and oceans on glacier variability in Scandinavia will be further addressed.

Storglaciären, northern Sweden

One important issue in climatic studies is the impact of climate change or extreme weather events on society. Tree-ring data is a good proxy for past climates but it won't tell you how climate affected human society in the past. In a 2005 study, tree rings and a farmer's diary were combined to reconstruct a prolonged drought in southern Sweden in the early 1800s. In a Sida/SAREC supported project in Shaanxi province, China, we looked at past drought and monsoon variability and its effect on society by combining tree-ring data and historical records. This project also resulted in, among others, a reconstruction of Tibetan temperatures for the last 2400 years and the formation of the Sino-Swedish Centre for Tree-Ring Research (SISTRR).

Huashan Mountains, China (photo by Petter Stridbeck)

Being part of the RCG the Department of Earth Sciences, University of Gothenburg, plays a vital role in my research. This group has thorough knowledge of statistical analyses, modelling and up/downscaling etc. When using tree-ring data for climate reconstructions it is important to determine the stability in time of the climate-tree growth relationship, but also identify the regional significance of the signal. Thus by using the existing statistical knowledge within the RCG it is now possible to make rigid tests of the strength and stability of this climate-tree growth relationship on different time scales, much like previous studies conducted by the group.

I have been involved in three of large EU funded projects (ADVANCE 10K, EMULATE and now Millennium), and through these I have created a network of European collaboration partners, some who are leading scientists in climatology, e.g. Prof. Keith Briffa and Dr Juerg Luterbacher. Through my postdoctoral fellowship/visiting scientist position at the National Climate Centre in Beijing, China, I have made contacts with some of the leading dendroclimatologists and paleoclimate modellers in China, and presently we have several joint Swedish-Chinese paleoclimate projects, where regional patterns of climate variability will be compared on short and long timescales during the past millennia using proxies and paleoclimate models.